[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P25] Three-dimensional thermomechanical modelling beneath Guerrero, Mexico, and its relation to the occurrence of interplate seismic phenomena

*末永 伸明¹、吉岡 翔一^1,2、Vlad Manea³、Marina Manea³、Erika Moreno¹、季 頴鋒^4,5 (1.神戸大学都市安全研究センター、2.神戸大学大学院理学研究科惑星学専攻、3.メキシコ国立自治大学地球科学研究所計算地球力学研究室、4.中国科学院チベット高原研究所、5.中国科学院大学)

キーワード：3次元熱対流モデリング、プレート境界面温度、スラブ内含水量分布、スロー地震

In this study, we investigated the relationships among the occurrence regions of megathrust earthquakes and slow earthquakes, estimated interplate temperatures, and dehydration processes at the plate interface in the subduction zone of the Cocos plate in Mexico, with a focus on the Guerrero seismic gap. For this purpose, we performed a series of 3-D thermomechanical numerical simulations of subduction based on a combination of multiple unknown model parameters. Comparing the temperature field for the optimal model with the occurrence region of the interplate seismic phenomena, the temperature along the slab surface where megathrust earthquakes tend to occur is estimated to range from 200 to 400 °C. In addition, the occurrence areas of recent long-term slow slip events (hereafter referred to as L-SSEs) with a recurrence interval of ~4 years in the range where the amount of slip is 10 cm or more correspond to a temperature range of 350 °C to 550 °C outside the Guerrero seismic gap region. On the other hand, in the Guerrero seismic gap region, L-SSE slip is observed up to shallower areas, but the updip limit temperature in the region with the largest slip amount (~14 cm) is also estimated to be approximately 350 °C. Furthermore, for regions affected by tectonic tremors (hereafter referred to as TTs) within seaside swarms and inland swarms, our temperature estimates range from 500 °C to 570 °C and from 600 °C to 700 °C, respectively. Finally, we compared the estimated dehydration processes on the plate interface for the optimal model with interseismic events. These findings suggest that considerable dehydration from MORB within the oceanic crust and ultramafic rock within the slab mantle occurred near long-term slow slip events and tectonic tremor regions.